(538a) A Novel Power Cycle Integrated With Post Combustion CO2 Capture Process Using LNG Cryogenic Exergy

Recent
climate change and related disasters have attracted worldwide attention and
brought efforts to reduce greenhouse gases especially for CO₂. Among
the various sources of the CO₂ emission, power plants combusting
fossil fuel such as coal, oil and gas contribute to the CO₂ emission
the most ¹.
Several techniques to remove CO₂ from the power plant flue gas have
been proposed, and amine based CO₂ absorbing systems are considered
the one of the most suitable options because it has been demonstrated as the
most mature and less expensive technology ².
However, the large energy consumption and corresponding electricity cost increment
have been pointed out as the obstacle of the commercialization. The estimated cost
of CO₂ capture increases the cost of electricity production by 40–85%
for a supercritical pulverized coal power plant. ³
In this study, a novel pulverized coal (PC) power plant integrated with CO₂
Rankine cycle utilizing Liquefied Natural Gas (LNG) cryogenic exergy has been
proposed. By utilizing the latent heat of low quality steam which originally
wasted in the steam condenser, this process is able to extract additional power
from the CO₂ Rankine cycle.

Figure.
1 Process Flow Diagram of Novel Power Generation Cycle

Figure
1 gives a principal process scheme of the novel power generating process
proposed in this study. The four main parts of the process are the steam cycle,
CO₂ capture process, gas conditioning process and CO₂
Rankine cycle integrated with LNG gasification process. Flue gas pathway is
similar to the conventional power plant with post combustion CO₂
capture process. The CO₂ generated from the PC power plant is delivered
to the Rankine cycle through CO₂ capture and gas conditioning
process. Steam pathway is, however, somewhat different from the conventional
cycle. Both the steam condensate and low pressure steam are utilized for the CO₂
Rankine cycle superheating. The steam condensate (C-1) from the Feed Water
Heater (FWH) (23) is directed to preheater and the low pressure steam (S-1) id introduced
to CO₂ super heater (41) in CO₂ Rankine cycle. In this
process, Cryogenic Exergy of LNG is utilized for CO₂ condensation
integrating it with LNG gasification process. In addition, the steam from the
low pressure turbine, in contrast to the conventional steam cycle, is condensed
in the CO₂ super heater in the CO₂ Rankine cycle. In this
manner, the latent heat of the steam which is originally wasted in conventional
steam cycle can be utilized for CO₂ super heating and the amount of
power generation of entire plant is eventually increased. Total Energy production of the steam
cycle and CO₂ Rankine cycle without integration is turns out to be
70.75 MW_e. On the other hand, total energy generation in the novel
process is increased to 80MW_e by utilizing the wasted low pressure
steam. It is about 20 % increment of the total power production. The exergy
efficiency of the CO₂ Rankine cycle increases from 0.34% to 40% by
integrating steam cycle with CO₂ Rankine cycle. Using the integrated
power cycle, the fuel cost for the power production can be lowered to only 61%
of the conventional steam cycle from 12.8 Euro/MW to 7.81 Euro/MW.

This research was supported by a grant
from the LNG Plant R&D Center funded by the Ministry of Land,
Transportation and Maritime Affairs (MLTM) of the Korean government.

1.         Abu-Zahra,
M. R.; Schneiders, L. H.; Niederer, J. P.; Feron, P. H.; Versteeg, G. F., CO₂
capture from power plants: Part I. A parametric study of the technical
performance based on monoethanolamine. International Journal of Greenhouse
Gas Control 2007, 1 (1), 37-46.

2.         Rao,
A. B.; Rubin, E. S., A technical, economic, and environmental assessment of
amine-based CO₂ capture technology for power plant greenhouse gas
control. Environmental Science & Technology 2002, 36
(20), 4467-4475.

3.         Abu-Zahra, M. R.;
Niederer, J. P.; Feron, P. H.; Versteeg, G. F., CO₂ capture from
power plants: Part II. A parametric study of the economical performance based
on mono-ethanolamine. International journal of greenhouse gas control 2007,
1 (2), 135-142.